Backswing: Use immediately after performing an attack to chose any number of figures affected by that attack. Each of those figures tests Awareness. If none of the figure pass, each chosen figure suffers 2 Heart and is Stunned. Regular minion Troll has no ability to attack more then 1 figure (overlord cards or other such interactions aside), ability text is clear, only heroes affected can then be targeted by backswing.
You are correct That said, if another interaction allowed the troll to target multiple heroes with its attack, backswing would be applicable.

Got to say, the usual snowball Descent arguments are running through, if not directly popping up, in this to me. Conditions are a very conditional (aha!) part of the game but undeniably powerful. The overlord has reliable access to them via open groups (which can let you virtually guarantee that you can get one that you want) or overlord class cards, but heroes can arguably benefit from them more because pinning that must kill monster (quest related lieutenant or something that must not do something this turn) is a game winner, while immobilizing 1 hero dosent stop the other 3. Overlord cards are obviously game winners but they are random, im sure every overlord here has had at least one game crying out for a frenzy or dash to be here, in my hand, right !"£$ing now, and a few classes or characters can hard counter them through ability or feat (dangers sense and elder Mok say hi off the top of my head). Quest are swingy by nature in this game, the hero/class/monster/item combinations, while not infinite, might as well be for practical purposes. A while back my group played back to back shadow rune campaigns and the interlude was like 2 different quests - first time around heroes cake walked it against an experienced overlord, 2nd time around got curb stomped by the relatively new OL player. Obviously group plans tend to solidify over time, and players usually become accustomed to a style of play or role, you said you rotated out with another overlord player but what would happen if a third player took up OL duties? Do they make vastly different choices for open groups? Do they ALWAYS pick web trap (I never leave my evil lair without it, even if the heroes are well attributed to pass it). Do they look at the last campaign and build a strategy that might have been good in the last setting but is now not useful against the current hero group? What happens when the regular healer player is asked to play a scout? Do they look to play the same or do they try and adapt to a new role, and if so does the **** impact their decisions in regards not only to play but skill purchase and equipment picks? (does the last campaign of being web trapped every.single.encounter, drive them to counter immobilize when i am no longer actively using it?) And al of this before any player skill is brought into question. (inaccurate rules implementation that costs quests aside, that could have an epic stanza for itself) The game can snowball immensity, i think everyone on these boards has seen it - but wishing that the quests where 'balanced' is a pipe dream, the variables are simply to many to extrapolate before it get lost in tedium. For the most part my games have had balanced games and wildly swingy quests. And even then the group loves it al the same. Acceptance that some quests are likely to be un-winnable only makes that unexpected success all the sweeter.

hmm... oh so that is why I was constantly loosing a 2 heroes game to a newbie overlord...
I really do like Descent, but introducing a mayor rule change 4 years after release smells like something is seriously wrong with this game.
Its hard to say whats causes people to lose in descent - there are so many variables including number of players, class choice, hero choice etc, before you even get to the respective skill of the individual players.
Simple maths however determines that fewer heroes struggle due simply to action economy.
2 heroes have 4 actions a hero round (abilities/feats/skills not withstanding). Looking at the original Shadow rune intro quest a the overlord would have 1 ettin and 3 goblin archers, 8 actions in his turn.
Now consider that each attack has a 1/6 (or thereabouts chance to miss) which essentially wastes an entire action which hurts a LOT more when you only have a 4 a turn.
Then consider that without a healer the heroes have very few ways to recover damage so if 1 of your 2 heroes isn't fixing you up your going to end up getting knocked down a lot (which wastes an entire turn if your partner cant pick you up.)
The game is essentially balanced and built around 4 heroes, the 3 player variant is usually in the heroes favor - for similar reasons - and the faq amendments address the biggest issue 2 hero games had quite well, the free regular attack or 2 heart recovery lets the heroes do more but not spam more powerful abilities.

The rule was introduced with Heirs of blood for balance issues. 2 heroes is widely acknowledged as being the hardest balance for heroes to deal with. Action economy is a premium in descent and 2 heroes usually struggle to actually get stuff done.

I'll disagree with that. Unless you're fighting a very specific monster (e.g., elemental or lieutenant) who can do a second valuable action while already in contact with you, it is useless. And a if you have your starting weapon (which is our case), you're are pretty short on surges - and I'd rather use it to recover a fatigue/health. I find that defense training would be a great combo with the Defense and Chainmail: Brown + Gray + Gray + guaranteed Shield. And it also combos very nicely with Leoric's ability.
You dont find stunning mobile monsters or large blocking monsters to be valuable? Descent has such a huge section of the game revolve around mobility and action use that i have always been able to find a use for it.
Yeah, monsters only get one attack on a regular turn but you can move in, stun and move away, if it is a melee monster now it has to move, if its a range monster it can attack but cant get away.
Or you can move in stun an enemy and keep it form moving twice, in a hunt a lieutenant (or specific monster) quest thats pretty dam,n sweet.
BH i have found it to have much more mileage then defend - although suppose it depends on how squishy the rest of the team is/how much healing you can pump put.
But thats the beauty of descent, hero, class, skill and weapon combinations are always very fluid.

Advance will shine the more you use it and get used to when to time it, between oath of honor and advance you can move 7+spaces for free (assuming a speed 4 character) and get 3 attack actions. There isnt much in the game that offers that level of action economy and in a game that is largely about action economy that is huge. Defend largely finds itself consigned to my 2nd rate or lower picks - its not bad per say but shield slam is obscenely powerful (again, action denial is super good) and i loath to pass it up. The defensive style is good for some quests but in my experience anything where moving is a priority it starts to fall apart quite quickly because its just not fast enough to keep pace. (Admittedly Syndraels feat offsets this wonderfully. )

As the others have mentioned the monsters can be put into any campaign via open groups. However the only quests where they will be a default monster group are the 2 rumor quests that come in the pack. A bit of research can be used to go over the campaign you are planning to play and the monsters that come in a pack to see how often they will be available. (Not that i have but im sure someone probably has done). On a different note, are there any European, specifically UK, players who have been able to get a hold of treaty of champions? All my usual regular and reliable stockists have not seen the product. Best i have found is an Amazon seller going for £40+ which is bonkers.

Tell that to our skirmisher who once missed on 7 out of 12 rolls in a single encounter! (It was at that point I did an analysis of the weight of each face of the blue die based on the volume carved out of each side to determine if it was naturally loaded.)
What was the scientific result of this research? I am generally curious as some of my players have muttered about this over a few games.

Pincer move is best option. 2 heroes back track to the fire pit (via caravan) 2 heroes push to the ruins and kill goblins and block barghests from running in circles. Send avric and either Loeric or Jain hunting and have Syndarel be primary camper with the other supporting. Its a OL favored quest, and a heavily favored one one at that, but it looks winnable for the heroes. The reverse of first blood really (but at least the heroes have a possible chance, unlike first blood where the OL is doomed). Would love to hear other peoples experiences.

Best strategy i can see at a glance is for heroes to rush Goblins and eliminate them (with that party composition it should be possible - terrible rolls aside), The goblins re-spawn end of round so will in most instances sit there getting mulched without ever doing anything if heroes are present. First hero Turn Syndarel pops feat and use it with Loeric. Depending on goblin placement may be able to stamina move up and attack twice or may have to move+stamina attack once. Leoric, then stamina move and attack twice if range is good or move and stamina and attack once. Then Jain pops feat and scoots up and attacks twice (once from feat) Avric is carrying acolyte as he has no range weapon and wont be killing goblins. Alternatively send Jain Fist with feat, then use Syndarel and see if you can position jain to abuse oath of honour to pop syndarel up. Optimistically and depending on placement of goblins they may all be dead or severely depleted. If all dead press heroes on to deal with barghasts and spawning goblins, if not send appropriate hero to back up avric in wiping out remaining goblins then get back to business of killing spawns. You will just have to deal with barghast attacking or running away as it comes up - the priority here are goblins for me, keep them under control and you can keep the barghasts running or wear them down.
Alternatively you could play cagey and let the OL advance goblins to the camp site, yeah, he gets 1 stamina token at the end of his turn but if there are 4 heroes all the goblins should die quickly and then he is in the same boat of spawning 2 at the end of turn. Either way make goblins die fast then kill re spawns fast
Unlike first blood in shadow rune though the OL gets a very realistic chance at this as the heroes have to be focused on pulping all goblins, even 1 or 2 getting by will cripple them quickly, but if the initial 5 are overwhelmed quickly the heroes can be reasonably happy to camp the lair and hunt down dead dogs at their leisure. This should be the next campaign i play so i will let you know how i fare - although i imagine we will be using different heroes and classes.

As a quick heads up seeing as the reinforcement issue was what was causing this, most quests in Descent allow only 1 monster to be reinforced from a group (a scenario might say, at start/end of turn reinforce 1 goblin and 1 open group monster). The scenario will always tell you which groups are allowed to reinforce and to what extent. Also look out for WHEN they reinforce, getting a monster at the stat of the OL turn and having it activate is a huge difference to it reinforcing at the end of the turn and being forced to wait a a turn to activate it.

Movement is a bit weird at the start of the descent learning process. Technically a move action does not actually make you move but gives you a pool of movement points equal to your speed.
This could be supplemented by then using stamina to add movement points or taking a second move action to add more movement points (bear in mind this can be done over the course of the turn). If terrain is impeding movement, like with a water space, then each space costs 2 points of movement to enter, if you only have 1 point you cannot pay the cost and cannot move into the water space. But as mentioned you can augment your movement pool (take a move action to get 5MP, then use 1 stamina for 1MP = 6MP or 3 water spaces. OR double move to have 10MP = 5 water spaces. Unfortunately I cant advise on the scenario as i dont have it in front of me.